Foundation Soil Volume Estimator
Calculate the exact amount of soil needed for your foundation project with our precise calculator.
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Note: These calculations account for soil compaction and include a 10% safety margin.
Frequently Asked Questions
Our calculator provides professional-grade estimates based on standard engineering formulas. It accounts for soil compaction factors and includes a 10% safety margin. For critical projects, we recommend consulting with a geotechnical engineer.
Different soil types have varying compaction characteristics. Clay soils, for example, compact more than sandy soils, meaning you’ll need more material to achieve the same volume. Our calculator adjusts for these differences automatically.
Measure the longest points for length and width. For irregular shapes, break them down into regular shapes (rectangles, circles) and calculate each section separately. Our L-shaped option helps with common foundation variations.
Excavation volume is the space you need to dig out. Soil volume is the amount of fill material needed, which differs due to compaction. Loose soil occupies more space than compacted soil, so you typically need more material than the hole’s volume.
Calculating Foundation Soil Volume
To provide context for the estimator’s functionality, here’s how to calculate soil volume for a rectangular foundation:
| Component | Formula | Description |
|---|---|---|
| Excavation Volume | Length (ft)×Width (ft)×Depth (ft) | Calculates the cubic feet of soil to be excavated for the foundation. |
| Bulked Volume | Excavation Volume×Bulking Factor | Estimates the volume after excavation, accounting for soil loosening. |
- Example Calculation:
- For a foundation 15 ft long, 10 ft wide, and 0.5 ft deep:
Volume = 15 x 10 x 0.5 = 75 cubic feet
Volume in cubic yards =75/27 approx. 2.78 cubic yards
- Bulking Factors (based on THS Concepts):
- Clay and Gravel: 1.15
- Sand: 1.05
- Loose, free-running soils (e.g., sand): 1.0–1.1
- Dense, cohesive soils (e.g., clay): 1.2–1.5
Practical Considerations
- Soil Compaction: If backfilling, add 10–20% extra soil to account for compression during compaction, as noted by Alluvial Soil Lab.
- Non-Rectangular Shapes: For irregular foundations, use advanced tools like the Volume Calculator for complex geometries.
- Soil Type: Different soils have varying densities and bulking factors, affecting excavation and removal planning:
- Easy Digging: Loose soils (e.g., sand, fine gravel)
- Medium Digging: Cohesive soils (e.g., clayey gravel)
- Hard Digging: Wet clay, gravel with boulders, or material requiring blasting
- Sloped Excavations: For deeper foundations, account for sloped walls to prevent collapse, increasing the excavation volume. Use trapezoidal prism formulas or consult engineers.